If you haven't seen it already, the technical data for the SRF05 on the Robot Electronics website is quite useful.
The link is: http://www.robot-electronics.co.uk/htm/srf05tech.htm
You don't need to use any ports as there is no serial interface on the SRF05. All you need to do is measure the length of a pulse output on the "echo" pin. The length of the pulse is proportional to the distance of the object.
A typical sequence might be:
1. send out a trigger pules to the SRF05,
2. wait for the rising edge on the echo pin,
3. start a counter running,
4. wait for a falling edge - stop the counter,
5. read the counters value and calculate the distance